1. Field of the Invention
The present invention relates to a friction plate for a multiple disc lock-up clutch used for a torque converter for an automatic transmission of a motor vehicle or the like equipment.
2. Related Background Art
In general, a friction plate for a multiple disc lock-up clutch used for a torque converter is manufactured by fixing a plurality of friction material segments to one face or both faces of a ring-shaped core plate in the circumferential direction thereof, and is used as a plate on the drive side, that is, a drive plate in the lock-up clutch.
FIG. 14 is a partially enlarged view of a side face of a conventional drive plate, that is, a friction plate 150. The friction plate 150 is configured by fixing a plurality of friction material segments 152 on both faces of a core plate 151. A gap is formed between the friction material segments 152 of the friction plate 150, and this gap provides an oil groove 153 for permitting communication between an inner peripheral edge and an outer peripheral edge. The oil groove 153 is provided to restrain clutch judder.
An impeller of torque converter, which is connected directly to an engine, is in a state of rotating normally. Therefore, an oil pressure of about 0.5 kgf is always present, so that some pressure is applied to the drive plate and a separator plate even if a piston of multiple disc lock-up clutch is not operated. This pressure presses the drive plate and the separator plate against the piston side to bring these plates into contact with each other, so that drag torque is produced. Also, the oil groove provided for restraining judder has a high oil discharging property, and has a tendency to respond sensitively to the above-described pressure to further increase the drag torque.
Also, an edge portion 154 at the end of the conventional friction material segment 152, which defines the oil groove 153, is substantially at right angles to the core plate 151. Therefore, it is difficult to form a desired oil film in the vicinity of the oil groove 153, so that the drag torque is liable to increase.
Accordingly, an object of the present invention is to provide a friction plate capable of reducing drag torque produced between the friction plate and the mating friction face.
To attain the above object, the present invention provides a friction plate formed by fixing a plurality of friction material segments on a core plate, in which an edge portion opposed to the mating member of an end portion of the friction material segment extends from the inner periphery side to the outer periphery side and has a cross-sectional shape in the axial direction formed of a curved face.
Also, the present invention provides a friction plate formed by fixing a plurality of friction material segments on a core plate, in which an edge portion opposed to the mating member of an end portion of the friction material segment extends from the inner periphery side to the outer periphery side and has a cross-sectional shape in the axial direction formed of a curved face, and the edge portion has dimensions in the range of 1% to 60% of the thickness of the friction material segment.
According to the friction plate in accordance with the present invention, since the curved edge portion is provided at the end of the friction material segment, a necessary oil film is produced between the friction plate and the mating friction face, so that drag torque can be reduced by this oil film.
Also, since a press molded groove is provided, a necessary oil film is produced between the friction plate and the mating friction face, so that drag torque can be reduced by this oil film.